The present invention relates to a high speed character matcher and method.
In the fields of optical character recognition, facsimile compression and image correlation, it is necessary to determine the degree of similarity between characters. The characters are typically represented by a pattern of digital picture elements (pixels). In order to determine whether a pair of characters are similar enough to declare a match, a comparison is performed upon the pattern of pixels.
One prior art approach, known as the "raw exclusive-OR" error, utilizes a template or pattern matcher which calculates the degree of similarity between a pair of patterns by summing the number of elements for which the patterns are unequal. This technique is usually normalized in such a way as to make it invariant to the size of the patterns being compared. A major problem with such a prior art template matcher is that it treats all errors alike regardless of where they occurred.
Another prior art approach, known as the "rubber mask" technique, attempts to match a pair of patterns by geometrically distorting one pattern so as to achieve geometrical conformity with the other. This prior art technique is ambitious in that it attempts to compensate for large distortions by actually warping one template or pattern to fit the other. While the "rubber mask" technique can deal with severe distortion, because of its complexity, it is quite difficult to implement in high speed digital hardware.
Therefore, there is a need for an improved character matcher and method that can be easily implemented into high speed digital hardware.
In view of the above background, it is an objective of the present invention to provide an improved high speed character matcher and method for use in the fields of optical character recognition, facsimile compression and image correlation.